The present invention relates to processes for manufacturing upholstered chair cushions with sculpted effects on them.
Conventionally, chair cushions have been made by hand. Sculpting effects are achieved by placing the upholstery fabric over a thin foam topping layer and a thick cushion, and tying the layers together at selected locations with button tufting and/or sewn seams. The manual labor required is naturally quite expensive and time-consuming.
There have been numerous attempts to develop a simple, economical automated process for producing upholstered cushions. Many processes employ vacuum molds to drawn upholstery fabric into desired shapes. But a vapor impervious elastomeric backing sheet must generally be used to draw a vacuum on fabric. When the backed sheet of fabric is in a completed cushion, however, the cushion feels "hot" to the skin since it does not let the cushion breathe. The backing sheet can sometimes be eliminated when the fabric has a tight weave, but many tight weave fabrics feel hot, and many popular stylish fabrics are not tightly woven. Art representative of such processes include Sanson et al., U.S. Pat. No. 4,116,736 entitled "Method of Making a Foam Plastic Cushion Having a Peripheral Frame and an Exterior Cover" issued Sept. 26, 1978.
Others have tried to eliminate the hot feel of such vapor impervious upholstered cushions by using matingly configured dies and heat to shape the fabric. The underlying cushion is preshaped and then bonded to the shaped fabric to form the completed upholstered cushion. One way to shape the upholstered cushion is to injection mold the cushion from a foamed material, but when a cushion is injection molded, it forms a skin which is substantially vapor impermeable and hot to the feel. It feels generally much harder to sit on and feels less soft and pliable to the touch. Another way is to cave the cushion from a block of foam, but this is time-consuming, and often does not produce a cushion which accurately fits the shaped fabric. A third way to provide cushion which conforms accurately to the shape of the shaped fabric is to injection mold the cushion inside the fabric, but a hot skin is still formed. In addition, the foam polymer can wick into fabrics, bind the fabric filaments together, and give a rough feel to the fabric. Art representative of such processes include Urai et al., U.S. Pat. No. 4,107,829 entitled "Method of Manufacturing Seat Cushions" issued Aug. 27, 1978.
Finally in order to conform to the desired shape, an elastic fabric must be used. Such fabrics have a look and feel that may not be acceptable in many applications.